Obliterating sign type carrier for typewriting or similar machines

ABSTRACT

A type carrier for typewriters is provided with a printing surface for printing an obliterating sign formed of an edge zone having a constant width and adjacent to the external edge of the printing surface and an inner zone. Both zones are knurled by means of parallel and equidistant grooves perpendicular to the longer edge of the printing surface.

United States Patent Rava et a1. Nov. 20, 1973 [54] OBLITERATING SIGN TYPE CARRIER FOR 3,166,008 1/1965 Lewandoski 101/397 X TYPEWRITING R SIMILAR MACHINES 3,202,257 8/1965 Rihm 197/36 1,878,516 9/1932 Heene 101/398 X Inventors: Sergio Rava, C Arturo Rolfo, 2,506,746 /1950 Simms 101/399 x Murisengo, both of Italy 2,317,170 4/1943 Bastow et a1. 1. 197/36 525 754 9 1894 Weaver 101 399 [73] Assignee Olivetti & C9 Twin), 640:254 1/1900 Anderson... 197/1141 x Italy 935,519 9/1909 Kavle 101/399 1,402,935 1/1922 Hutson et a1. 10l/401.1 X [22] 1971 1,718,921 6 1929 Freund 101/401.2 x [21] APPL 9,714 1,814,758 7 1931 McCarthy... 101 401.1 1,905,118 4/1933 Nadell 197/181 1,961,644 6/1934 Sampson 101/399 UX Foreign Application Priority Data Jan. 21, 1970 Italy 67159 A/ Primary Examiner EmeSt T w i h Jr.

Att0rneyBirch, Swindler, McKie & Beckett [52] US. Cl 197/36, 197/181, 101/398 [51] Int. Cl B4lj l/04 [58] Field 6: Search 197/36, 37, 180, [57] ABS C 197/181; 101/396 A type carrier for typewriters is provided with a print- 401A 4016 ing surface for printing an obliterating sign formed of an edge zone having a constant width and adjacent to [56] Reerences C'ted the external edge of the printing surface and an inner UNITED STATES PATENTS zone. Both zones are knurled by means of parallel and 2,142,761 1/1939 Quinn 197/181 equidistant grooves perpendicular to the longer edge 2,258,189 lO/1941 Meisner 197/36 X of the printing surface, 2,662,455 12/1953 Freund 101/399 X 3,006,317 10/ 1961 Showalter 101/401 X 4 Claims, 5 Drawing Figures PATENTED NOV 2 0 I975 a fig:

PRIOR ART Fig. 2

INVENTORS SERGIO RAVA ARTURO F0 BY BIRCH, Swmmee Km 4 BscKeTf ATTORNEYS OBLITERATING SIGN TYPE CARRIER FOR TYPEWRITING OR SIMILAR MACHINES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a type carrier for typewriting or similar machines, particularly to type carriers for printing an obliterating sign having a relatively large printing surface.

The printing quality of a character on the paper is becoming more and more important for typewriters as well as for other kinds of office printing machines, in view of the development of the automatic character recognition, and particularly of the optical character recognition.

The apparatuses for optical character recognition require that characters to be read have both a clear edge, and a predetermined minimum coverage coefficient, that is the percentage of the surface covered by ink with respect to the entire surface of the character. Therefore both requirements indicate substantially the printing quality, which in any case improve as the portions of the sign covered by ink increase.

Where the character is formed of thin lines, a satisfactory printing quality can be reached by choosing a platen rubber having a suitable hardness, and a suitable impact force intensity, and/or by choosing the most appropriate kind of paper and ink ribbon. However, when an obliterating character is formed, thick lines or zones must be used in order to cover any type of character, for instance the boldface or extrabold characters as well as some type fonts for character recognition, and in such cases the inner portion of the sign often has large areas not covered by ink.

2. Description of the Prior Art Present in the prior art is a type carrier for bold face printing, where the edges of each line of a character project with respect to the inner part of the printing surface. Even if this type carrier is able to print obliterating signs having satisfactory edges, it is unable to produce signs having a sufficient coverage coefficient.

It is also known to use type carriers having a printing surface generally roughened as, by striking it against sand paper or by means of other sanding treatment, in order to increase the friction coefficient thereof. Even if this provision increases to some extent the coverage coefficient, this type carrier is not able to produce a completely satisfactory printing quality, particularly in the case of characters formed of very thick lines.

SUMMARY OF THE INVENTION The main object of the invention is to provide a type carrier for typewriting or similar machines that print by means of ink or carbon ribbon, which is capable of producing printed obliterating signs having very clear edges and a very high coverage coefficient.

According to the invention we now provide a character obliterating type carrier for typewriting or similar machines, having a relatively large printing surface, wherein the improvement comprises knurling at least a part of said printing surface to provide a set of parallel and equidistant grooves having a depth less than 0.05 mm and a pitch less than 0.05 mm.

A preferred embodiment of the invention is now described by way of example and not in a limiting sense.

DESCRIPTION OF THE DRAWING FIG. 1 is .a longitudinal section of atypewriter type carrier according to the invention, in a very enlarged scale;

FIG. 2 is a front view of the type carrier of FIG. 1;

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is an enlarged view of a character printed with a conventional type carrier according to the prior art having a smooth printing surface;

FIG. 5 is a similar view of the same character printed with a type carrier having type face according to the in vention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is disclosed as embodied in a type carrier adapted to be mounted on a type bar of a conventional typewriter. The character to be printed is the conventional obliteration sign included in a conventional type font for optical character recognition. This sign is of a rectangular shape designed to fully cover any other character of the type font.

It is intended that the type face according to the invention can be embodied in any kind of type carrier, for instance, typewheels, type sectors, type drums, spherical type carriers, etc.

With reference to FIG. 1 of the drawing, the numeral 6 generically indicates a conventional type carrier, which is provided with a pair of wings 7 adapted to be secured, for instance by soldering, to a type bar of a typewriter, not shown in the drawing. The type carrier 6 is provided with a pair of type faces 8 and 9, in correspondence with the lower case position and the upper case position respectively. In the embodiment now disclosed the two type faces 8 and 9 (FIG. 2) are similar and each will present an obliterating sign 30 of a type font for optical character recognition. Each of the type faces 8 and 9 is intended to print a completely filled rectangular area, that will cover any other character erroneously printed.

As it is known, the printing surface of a conventional type is normally formed by coining a block of soft steel. The printing surface of each sign of the conventional type carrier is cylindrical and has a curving radius equal to the radius of the roll platen, where it has to impact for printing. In any case the so formed type face is normally smooth.

The printing done by a conventional smooth type face produces a sign 20, which in an enlarged scale is substantially like that shown in FIG. 4. It should be noted that the edge 21 of the sign 20 is very indistinct, cut out and discontinuous. Some inked portions are even completely separated from the main part of the sign 20. Furthermore it should be noted that at a certain distance from the edges 21 of the sign 20 there are large zones 22 uncovered by the ink. It has been found that it is impossible to eliminate the uncovered zones 22 by simply changing the roller platen or the ribbon or the paper, or by increasing the intensity of the impact force.

According to the invention, type faces 8 and 9 are coined so as to form an edge zone 11 (FIG. 2) having a constant width and an inner zone 12 surrounded by the edge zone 11. The edge zone 11 is depressed with respect to the inner zone 12 a distance of about 0.015

mm. Therefore, the edge zone 11 appears as a rectangular frame around the inner zone 12.

The width of the edge zone 11 is no more than onefourth of the width of the obliterating sign 30 and corressponds to the part of the sign 20 of FIG. 4, where the uncovered portions 22 are rather reduced or absent, whereas the inner zone 12 (FIG. 2) corresponds to the part of the sign 20 of FIG. 4 where the uncovered portions 22 are crowded. Preferably the width of edge zone 11 (FIG. 2) is substantially equal to one-fifth of the width of the sign 30.

After the coining, the type carrier 6 is hardened in a known manner. Subsequently, before soldering the type carrier 6 to the type bar, (not shown) both the edge zone 11 and the inner zone 12 are knurled, for example by means of a suitable milling tool. The knurling provides a set of lines or grooves 13 (FIG. 1) mutually parallel and equidistant. The grooves 13 are preferably perpendicular to the length of the sign 30.

As far the size of grooves 13 is concerned, it has been found that a high printing quality can be obtained if the grooves 13 have both a depth and a pitch less than 0.05 mm. In the present case, shown in the drawing, the grooves 13 have a depth of about 0.01 mm and a pitch of 0.0l mm.

The so knurled type faces 8 or 9 when tested under the same conditions as the prior art device which produced sign 20, produced a sign which in an enlarged scale is shown in FIG. 5. It should be noted that the edges 31 of the sign 30 are much more distinct than edges 21 of sign 20 and that no uncovered portions 22 are produced. It should also be noted that a very high uniformity of coverage by ink, or colour intensity, between the peripheral portion and the central portion of the sign 30, has been obtained. Therefore, an apparatus for optical character recognition cannot recognize the previously printed character, wherein the improvement comprises:

a. an edge zone of constant width adjacent to and inside the entire perimeter of said printing surface, said edge zone lying in a first plane,

b. an inner zone surrounded by said edge zone, said inner zone lying in a second plane spaced from said first plane a constant distance so that said edge zone is depressed with respect to said inner zone by said constant distance around the entire perimeter of said inner zone,

. a set of similar grooves mutually equidistant from one another provided on both said edge zone and said inner zone, said grooves being parallel to the shortest side of said rectangular printing surface.

2. A type carrier according to claim 1, wherein said equidistant grooves have a depth and a pitch both less than 0.05 mm.

3. A type carrier according to claim 1, wherein said equidistant grooves have a depth of substantially 0.01 mm and a pitch of substantially 0.015 mm.

4. A type carrier according to claim 1, wherein the width of said edge zone is more than the depth of said grooves and less than one-fourth of the width of said printing surface. 

1. A character obliterating type carrier for optical character recognition typewriting or similar machines that print on a paper sheet by striking an ink ribbon, said type carrier having a substantially rectangular printing surface for fully covering with ink any other previously printed character, wherein the improvement comprises: a. an edge zone of constant width adjacent to and inside the entire perimeter of said printing surface, said edge zone lying in a first plane, b. an inner zone surrounded by said edge zone, said inner zone lying in a second plane spaced from said first plane a constant distance so that said edge zone is depressed with respect to said inner zone by said constant distance around the entire perimeter of said inner zone, c. a set of similar grooves mutually equidistant from one another provided on both said edge zone and said inner zone, said grooves being parallel to the shortest side of said rectangular printing surface.
 2. A type carrier according to claim 1, wherein said equidistant grooves have a depth and a pitch both less than 0.05 mm.
 3. A type carrier according to claim 1, wherein said equidistant grooves have a depth of substantially 0.01 mm and a pitch of substantially 0.015 mm.
 4. A type carrier according to claim 1, wherein the width of said edge zone is more than the depth of said grooves and less than one-fourth of the width of said printing surface. 